REVISED CALPUFF Modeling Report to Assess Impacts in Class I Areas

The proposed Rosemont Copper Project (Project) is a new copper project consisting of an open pit mine and associated processing facilities. The Project will be located in the Santa Rita Mountains approximately 30 miles southeast of Tucson, Arizona in Pima County. The “Rosemont Project, Mine Plan of Operations” was submitted to the Coronado National Forest in July 2007. The Coronado National Forest represents the Federal Land Manager (FLM) for purposes of the Environmental Impact Statement (EIS) that will be prepared for the Rosemont Project.

The FLM requested that an air impact analysis be submitted as part of the EIS to demonstrate protection and disclosure of impacts for regional Class I areas. The FLM requested that impacts be disclosed in relation to the National Ambient Air Quality Standards (NAAQS), Prevention of Significant Deterioration (PSD) Class I increments, and Air Quality Related Values (AQRV's), including visibility and total Sulfur and Nitrogen deposition.

In order to assess the requested impacts, the CALPUFF modeling system was utilized. CALPUFF represents the United States Environmental Protection Agency’s (EPA's) preferred model for the assessment of air quality impacts beyond 50 kilometers (km). As a result, CALPUFF was utilized to determine impacts at regional Class I areas that were located between 50 and 200 km from the Project. For each Class I area, CALPUFF simulations were produced for the various scenarios listed in the Draft EIS: Mine Plan of Operations, Phased Tailings Alternative, Barrel Alternative, Barrel Trail Alternative, and Scholefield-McCleary Alternative.